Separation of the propyl alcohols from water by azeotropic or extractive distillation

Abstract

Isopropanol and n-propanol cannot be completely separated from water by conventional distillation or rectification because of the minimum boiling azeotrope. Isopropanol and n-propanol can be readily separated from water by using azeotropic or extractive distillation. Typical examples of effective agents are: for isopropanol by azeotropic distillation, vinyl n-butyl ether; by extractive distillation, polyethylene glycol; for n-propanol by azeotropic distillation, amyl formate; by extractive distillation, n-butyl acetate.

We claim: 
     
       1. A method for recovering isopropanol from a mixture of isopropanol and water which comprises distilling a mixture of isopropanol and water in the presence of about one part of an extractive agent per part of isopropanol-water mixture, recovering water as the overhead product and obtaining the isopropanol and the extractive agent from the stillpot, wherein said extractive agent consists of one material selected from the group consisting of methyl benzoate, butyl benzoate, 3-pentanone, 4-methyl-2-pentanone, 2-pentanone, methyl isoamyl ketone, n-butyl acetate, 3-methyl-2-butanone, ethylene glycol methyl ether, n-amyl acetate, isobutyl acetate, propyl butyrate, isobutyl isobutyrate, n-hexyl formate, butyl butyrate, ethyl butyrate, ethyl caproate, hexyl acetate, mesityl oxide, propylene glycol isobutyl ether, 2-undecanone, 3-octanone, 2-heptanone, propiophenone, and nitrobenzene. 
     
     
       2. A method for recovering n-propanol from a mixture of n-propanol and water which comprises distilling a mixture of n-propanol and water in the presence of about one part of an extractive agent per part of n-propanol-water mixture, recovering the water as overhead product and obtaining the n-propanol and the extractive agent from the stillpot, wherein said extractive agent comprises one material selected from the group consisting of nitrobenzene, methyl benzoate, butoxypropanol, propoxypropanol, diethylene glycol ethyl ether acetate, 2-heptanone, and ethylene glycol ethyl ether acetate. 
     
     
       3. A method for recovering n-propanol from a mixture of n-propanol and water which comprises distilling a mixture of n-propanol and water in the presence of about one part of an extractive agent per part of n-propanol-water mixture, recovering the n-propanol as overhead product and obtaining the water and the extractive agent from the stillpot, wherein said extractive agent consists of one material selected from the group consisting of n-butyl acetate, isobutyl acetate, and ethylene carbonate. 
     
     
       4. A method for recovering n-propanol from a mixture of n-propanol and water which comprises distilling a mixture of n-propanol and water in the presence of an azeotrope forming agent, recovering the water and the azeotrope forming agent as overhead product and obtaining the n-propanol from the stillpot, wherein said azeotrope forming agent comprises one material selected from the group consisting of benzonitrile, mesityl oxide, hexyl acetate, amyl acetate, 3-heptanone, propyl butyrate, 4-methyl-2-pentanone and isobutyl butyrate.